Electric switch



Aug- 8, l939. P. M. cHRlsTENsEN 2,168,747

ELECTRIC SWITCH Filed July 6, `1.9558 2 Sheets-Sheet 1 FIF-Z. v5.5 E

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ELECTRIC SWITCH y Filed July 6, 1938 2 Sheets-Sheetl 2 .E u. f/

y Mtb 021275)/ Patented Aug. 8, 1939 UNITED STATES PATENT OFFICE 2.108.141 ELEc'rmc swrrcn Connecticut Application July 6, 1938, Serial No. 217,792

4 Claims.

The invention relates to electrical switches of the type wherein opposed contacts are adapted to be connected by a bridging contact supported by a movable contact carrying member.

The main object of the invention is to provide a switch in which the opposed contacts and bridging contact are constructed and mounted so that any burning of the contacts due to arcing is confined to those portions of the contacts which are not normally in contact, and so that the bridging contact rotates to some extent each time it is withdrawn from between the opposed contacts to thereby eliminate the concentration of the burning at one location.

From the following specication other objects and advantages will be apparent to those skilled in the art.

In the accompanying drawings I have shown the embodiments which I now deem preferable, but it will be understood that the drawings are intended for illustrative purposes only and are not to be relied upon as limiting or defining the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

In the drawings:

Fig. 1 is an elevational view of a switch embodying the invention, the cover for the casing being omitted.

Fig. 2 is a sectional view taken on the line 2-2 f of Fig. 1.

Fig. 3 is an enlarged sectional view taken on the line 3-3 of Fig. 1.

Fig. 4 is an enlarged elevational view of the contact carrier and contact.

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 4.

Fig. 6 is an elevational view of an alternative switch unit embodying the principles of the invention.

Fig. 'I is a view similar to that of Fig. 6 with a portion of the unit removed.

Fig. 8 is a sectional view taken on the line 8 8 of Fig. 6.

In the drawings I have illustrated the application of the principles of vthe invention to fused type switches having reciprocable contact carrying members, but the invention is obviously not limited to switches of this type.

Referring to Figs. 1-5, a casing I is provided in which is mounted/ one or more switch units 2 which may or may not be of similar construction. I have shown two identical switch units and it will, therefore, suiice to describe but one. Each switch unit comprises a base of insulating mate- (Cl. 20G-163) rial which is preferably mounted in the casing by means of screws 3. For facilitating manufacture, the base is made in two parts 4 and 5.

The part 4 is longitudinally slotted at 6, the bottom of the slot being grooved as indicated at 5 A contact 8 is located adjacent a recess 9 inone side wall of the slot 6 and is secured to the part 4 by a screw I0 extending upward through the part 4. A screw I0 serves as a binding post for connecting the contact 8 in a circuit. A secl0 ond contact II located in opposed relation to the contact 8 and adjacent a recess I2 in the opposite side wall of the slot 6 is secured in place by a screw I3 extending upward through the base. The contacts 8 and II may be made of spring 15 bronze and are preferably formed so that the depending portions located adjacent the recesses 9 and l2 have a limited resilient movement toward and away from each other, the recesses 9 and I2 allowing for the latter movement. I'he vertical 20 edges of the contacts are made somewhat divergent for reasons which will become apparent hereinafter.

The part 5 of the base is secured to the part 4 and its underside is formed with a groove I4 25 therein which is vertically aligned with the groove 1. Fuse receiving means, such as the clips I5 and I6, are preferably secured to the top of part 5 in any desired manner. The clip I5 is provided with a binding post II, while the clip I6 is pro- 30 vided with an offset portion I8 overlying and in electrical contact with a portion of the contact I I. A nut I9 threaded on screw I3 serves to hold the offset portion I8 in firm electrical contact with the contact I I and also aids in securing part 35 5 of the base to part 4. A screw 20 extending through part 5 and threaded into a bushing embedded in part 4 is provided for further securing the parts together.

A movable bridging contact 2| is provided for 40 making and breaking the circuit through the contacts 8 and II. In accordance with the invention the contact surfaces of the bridging contact are convex as indicated at 22, and the contact is so mounted that it is rotatable only about an 45 axis passing through its convex contact surfaces. The contact 2l is preferably, though not necessarily, a solid piece of conducting metal, such as brass, having a cylindrical portion 23. Contact 2| is carried by an insulating member 50 24 which is movable between contacts 8 and II, the member being slidable in the grooves 1 and I4 in the base. Member 24 has a circular aperture 25 formed therein which is sufiiciently larger in diameter than the cylindrical portion 23 of the 55 portion 3|.

2 bridging contact to permit the "free rotation vof the latter when it is mounted in said aperture.

Any desired construction may be used to prevent the separation of member 24 and the bridging contact. The now preferred construction-for this purposecomprises means, such as plates 24, se-g -cured to the member 24 and interlocked with the contact 2|. In the illustrated form, the interlocking is effected. by providing contact 2| with grooves 21 into which the plates 28 extend, the

-28 are so located with respect tothe contact 2| that they do not engage' with the bottom of the grooves 21, the side wall of aperture 28 thus serving as the bearing for contact 2| during its rotation relatively to member 24.

` Any suitable means may/be provided for effecting switch opening and closing movement of the member 24. In the illustrated switch an oper ating bail 28 is journaled in the casing side walls. The bail includes an offset or crank portion 28 positioned in/a recess 30 in the member 24, and it also includes an' externally located handle It is apparentv that oscillation of theihandle 3| will serve to cause reciprocation of the member 24 which in turn will move the contact 2| into and out of bridging relationship with the contacts 8 and When contact 2| is in its circuit closing position, as shown in Fig. 3, the contacts 8 and i resiliently press against it with a relatively high contact pressure per unit of contact area, the contacting areas being at approximately the center of the contacts 8 and and at the central portions of the convex end surfaces of the contact 2|. As contact 2| is withdrawn trombetween contacts 8 and and as actual physical engagement between contacts 8, |i, and 2| is broken, an electrical arc will be drawn between the edges of the contacts. Thus no burning or pitting of the normal contact areas will result. It has been found that contact 2| rotates very slightly about its own axis, which in the construction illustrated extends in the direction of the resilient movement of the contacts 8 and and always rotates in the same direction as it is withdrawn from between contacts 8 and for example, in the case of one switch tested, one complete revolution of contact 2| was effected for approximately every one hundred operations of the switch. Due to this rotation any burning or pitting of the peripheral edges of contact 2| will not be localized at one place, but will be uniformly distributed around the edges. The life of contact 2|., as measured by the number of times it can make and break a circuit before becoming too badly burned for efcient operation, is therefore much longer than that of a similarly contoured contact which is not rotatably mounted.

At present the'reason for the rotationl of theV bridging contact is not definitely known, but it is thought to be due to the edges of contacts 8 and gripping the bridging contact at points on its edges slightly below or above (as viewed in Fig. 3) a horizontal line through its center of rotation. Such gripping would exert an oicenter restraining force on the contact to thus cause it to rotate as it inally emerges from between the opposed contacts 8 and Such 0E- center gripping would result if the faces of the opposed contacts were not in vertical parallelism, which is probably the case. It has also been found that a new bridging contact when reciprocated in a switch not carrying current will The plates require a greater number of reciprocations to effect one revolution of the contact than when theswitchiscarr'yingcurrent. 'I'hlshasledtol thebelief that the slight hurting of the contact edges caused by arcing enhances the gripping ac on.

InFlgs.8,7,and8Ihaveshownanalterna tive form of switch imit embOdyln! the principles of the invention. While no casing or operating bail has been shown in these iigures it will be understood that the switch unit is adaptedtobemountedinacasingsimilartothat illustrated in Fig. 1 and is also adapted to be operated by a similar type of bail.

The insulating base of the switch unit preferably comprises two parts Il and I2. Part Il is slotted at I8, the slots being wider at one end than at the other. Contacts 54 are provided adjacent one side wall of the slots Il and are formed with offset portions 5i which are secured to the v contacts 54 in a circuit. Contacts 58 are located in opposed relation to contacts 54 and are secured in place by screws 58 threadedly engaged in holes inoilset portions Il. The contacts 54 and 58 are preferably formed of spring bronze and have limited resilient movement toward and away from each other. The bottoms of slots 53 are groovedas indicated at l As is apparent from Figs. 6 and 7, part 52 of the insulating base has a substantially greater projected area than part 5|. Fuse receiving means, such as the clips 42 and 83, are secured to the top surface of part 52. The clips 62 preferably include offset metallic conductors 64 which are clamped to contacts 58 by nuts 65. This clamping construction also serves to hold the parts 5| and 52 in assembled relationship. 'Ihe clips 43 include binding posts 58. The underside of that portion of the part 52 which projects beyond part 5|, is provided with grooves which cooperate with grooves 6| to form guide grooves.

Bridging contacts 81, similar to those shown in Figs. 1-5, are provided for making and breaking the circuits through the contacts 54 and 58. Contacts 61 are carried by reciprocable insulating members 88 and are secured thereto for rotation only about axes passing through their convex contact surfaces in any desired manner, although the construction illustrated is the same as that shown in detail in Figs. 4 and 5. The members 68 are adapted to be reciprocated in the guide grooves inthe base.

The remarks made above with respect to the operation of the embodiment shown in Figs. l-5 are equally applicable to the embodiment of Figs. 6, 7, and 8.

What I claim is:

l. In a switch, the combination of a base, a pair of spaced opposed contacts mounted on the base and having limited resilient movement toward and away from each other, a member movable between said contacts, and a bridging contact carried by said member for making and breaking a circuit between said pair of spaced contacts, said bridging contact having convex contact surfaces and being rotatable relatively to said member only about an axis passing through said convex contact surfaces.

2. In a switch, the combination of a base, a pair of spaced opposed contacts mounted on the base and having limited resilient movement toward and away from each other, a member movable between said contacts. and a bridging contact carried by said member for making and breaking a circuit between said pair of spaced contacts, said bridging contact having convex contact surfaces and .being rotatable relatively to said member only about an axis extending in the direction of the resilient movement of said pair of spaced contacts.

3. In a switch, the combinationfof a base, a pair of spaced opposed contacts mounted on the base and having resilient movement toward and away from each other. a member movable between said contacts. and a solid metallic bridging contact carried by said member for making and breaking a circuit between said pair of spaced contacts, said bridging contact having convex contact surfaces and being rotatable relatively to said member only about an axis passing through said convex contact surfaces.

4. In a switch; the combination of a base. a pair of spaced opposed contacts mounted on the base and having limited lifSillent movement toward and away from each othe rfa member, movable between said contacts. a bridging contact carried by said member for making and breaking a circuit between said pair of spaced contacts, said bridging contact having convex contact surfaces and being rotatable relatively to said member only about au axis passing through said convex contact surfaces, and means secured to said member interlocked with the bridging contact for preventing separation of the latter from said member.

PAUL M. CHRIS'I'ENSEN. 

